1. Field of the Invention
The present invention relates to a longitudinal adjusting device in motor vehicle seats, particularly for two-door motor vehicles. The backrest of the seat is connected to the seat portion through a joint fitting which may include an adjusting and securing device for the inclination of the backrest. The joint fitting includes a fitting component forming part of the seat portion and a pivotable fitting portion forming part of the backrest. One of the joint members has a pivot point about which the backrest can be swung forwardly after releasing a catch device. The seat portion is secured at running rails of a rail arrangement and each running rail is longitudinally displaceably arranged in a guide rail. At least one running rail is supported at the respective guide rail through a spring member such that the running rail is biased forwardly. At least one running rail includes a releasable locking device for the longitudinal adjustment, and the locking device includes a positioning device for making it possible to find or reset a previously adjusted longitudinal seat position.
2. Description of the Related Art
DE 44 23 634 A1 discloses a longitudinal adjusting device of the above-described type in which the positioning device includes another securing device by means of which, after the backrest has been swung forwardly and the seat has been pushed forwardly, a return swinging of the backrest into its position of use is prevented until the seat has once again reached its previously adjusted longitudinal position and is locked in this position. In this device, it is not possible without a previously modified adjustment of the longitudinal seat position, to place a load between the front seat and the rear seat, while still being able to transfer the front seat by a rearward swinging of the backrest and its locking device into a position of use. In addition, the positioning device and the securing device coupled to the positioning device are of cumbersome construction and substantially increase the cost of a vehicle seat equipped with such a device.
This is also true for the solution disclosed in EP 0 135 596 B1. In that solution, additional friction losses occur when forwardly swinging the backrest and forwardly pushing the seat because the running rail is constructed of two pieces and is composed of a forward transport rail and the support rail. Separate devices for connecting the running rail to the guide rail are required for both parts of the running rail which are displaceable relative to each other, so that a blocking device, on the one hand, and a locking device, on the other hand, are required. The blocking device is equipped with a positioning member which ensures that the positioned locking of the forward transport rail can only be effected when the backrest has once again assumed its position of use and the forward transport rail has reached during the backward swinging movement of the backrest once again a parallel position relative to the support rail. Only the forward transport rails on both longitudinal sides of the seat support the seat portion as well as the backrest. The requirement of having to provide for each part of the running rail, i.e., the support rail as well as the forward transport rail, a separate device for locking in longitudinal direction means that the device has a plurality of structural components which require substantial structural space.
Finally, in both solutions discussed above, the problem of reinforcing the forward movement during adjusting the longitudinal seat position by using spring members is not discussed, as is apparent from U.S. Pat. No. 3,931,995. Even though this problem is not discussed in the two above-described solutions, helical springs requiring additional structural space are also used in these constructions between the guide rails and the running rails.